KR102655346B1 - Image decoding method and device using chroma quantization parameters - Google Patents

Abstract

The video decoding method performed by the decoding device according to this document includes obtaining residual information about the current chroma block, CU chroma QP offset for the current chroma block based on the size and tree type of the current chroma block. Obtaining information, deriving transform coefficients for the current chroma block based on the residual information, deriving a chroma QP for the current chroma block based on the CU chroma QP offset-related information, The method includes deriving residual samples for the current chroma block by dequantizing the transform coefficients based on chroma QP, and generating a restored picture based on the residual samples.

Description

Image decoding method and device using chroma quantization parameters

This document relates to video coding technology, and more specifically, to a video decoding method and device for coding CU-level chroma quantization parameter offset-related information in a video coding system.

Recently, demand for high-resolution, high-quality video, such as HD (High Definition) video and UHD (Ultra High Definition) video, is increasing in various fields. As video data becomes higher resolution and higher quality, the amount of information or bits transmitted increases relative to existing video data. Therefore, video data can be transmitted using media such as existing wired or wireless broadband lines, or video data can be stored using existing storage media. When storing, transmission and storage costs increase.

Accordingly, highly efficient video compression technology is required to effectively transmit, store, and reproduce high-resolution, high-quality video information.

The technical task of this document is to provide a method and device to increase video coding efficiency.

Another technical task of this document is to provide a method and device to increase the efficiency of data coding for deriving quantization parameters for chroma components.

According to an embodiment of this document, an image decoding method performed by a decoding device is provided. The method includes obtaining residual information for the current chroma block, a coding unit (CU) chroma quantization parameter for the current chroma block based on the size and tree type of the current chroma block, Obtaining Quantization Parameter (QP) offset-related information, deriving transformation coefficients for the current chroma block based on the residual information, and calculating chroma for the current chroma block based on the CU chroma QP offset-related information. Deriving a QP, dequantizing the transform coefficients based on the chroma QP to derive residual samples for the current chroma block, and generating a restored picture based on the residual samples, The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block.

According to another embodiment of this document, a decoding device that performs video decoding is provided. The decoding device obtains residual information about the current chroma block, and calculates a coding unit (CU) chroma quantization parameter (Coding Unit (CU)) for the current chroma block based on the size and tree type of the current chroma block. Quantization Parameter (QP) An entropy decoding unit that acquires offset-related information, derives transformation coefficients for the current chroma block based on the residual information, and calculates conversion coefficients for the current chroma block based on the CU chroma QP offset-related information. It includes a residual processing unit that derives a chroma QP and dequantizes the transform coefficients based on the chroma QP to derive residual samples for the current chroma block, and an adder that generates a restored picture based on the residual samples. And, the CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block.

According to another embodiment of this document, a video encoding method performed by an encoding device is provided. The method includes deriving residual samples for the current chroma block, calculating a coding unit (CU) chroma quantization parameter for the current chroma block based on the size and tree type of the current chroma block. Parameter, QP) generating offset-related information, deriving a chroma QP for the current chroma block based on the CU chroma QP offset-related information, quantizing the residual samples based on the chroma QP to generate the current Deriving transform coefficients for a chroma block, generating residual information for the transform coefficients, and encoding image information including the CU chroma QP offset-related information and the residual information, The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block.

According to another embodiment of this document, a video encoding device is provided. The encoding device derives residual samples for the current chroma block, and calculates a coding unit (CU) chroma quantization parameter (Quantization) for the current chroma block based on the size and tree type of the current chroma block. Parameter, QP) offset-related information is generated, a chroma QP for the current chroma block is derived based on the CU chroma QP offset-related information, and the residual samples are quantized based on the chroma QP to generate the current chroma block. A residual processing unit that derives transform coefficients for and generates residual information for the transform coefficients, and an entropy encoding unit that encodes image information including the CU chroma QP offset-related information and the residual information, The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block.

According to another embodiment of the present document, a computer-readable digital storage medium is provided in which a bitstream including image information that causes image decoding method to be stored is stored. In a computer-readable digital storage medium, the image decoding method includes obtaining residual information about a current chroma block, and obtaining residual information about the current chroma block based on the size and tree type of the current chroma block. Obtaining information related to a Coding Unit (CU) chroma quantization parameter (QP) offset, deriving transformation coefficients for the current chroma block based on the residual information, and calculating the CU chroma QP offset. Deriving a chroma QP for the current chroma block based on related information, dequantizing the transform coefficients based on the chroma QP to derive residual samples for the current chroma block, and deriving residual samples for the current chroma block and generating a reconstructed picture based on the CU chroma QP offset, wherein the CU chroma QP offset information is signaled as a transform unit syntax for a first transform block among transform blocks of the current chroma block.

According to this document, even if the first transform block in the current chroma block does not contain a transform coefficient level other than 0, if at least one of the width and height of the current chroma block is larger than a certain size, information about the CU chroma QP offset can be signaled, Through this, the cost for configuring the decoding device can be reduced.

According to this document, even if the first transform block in the current chroma block does not contain a non-zero transform coefficient level, information about the CU chroma QP offset is provided in the transform unit syntax of the first transform block based on the size and tree type of the current chroma block. It can be signaled, and through this, the buffer requirements of the decoding device can be reduced and the cost for configuring the decoding device can be reduced.

1 schematically shows an example of a video/image coding system to which embodiments of this document can be applied.
Figure 2 is a diagram schematically explaining the configuration of a video/image encoding device to which embodiments of this document can be applied.
Figure 3 is a diagram schematically explaining the configuration of a video/image decoding device to which embodiments of this document can be applied.
Figure 4 shows an example of an intra prediction-based video/image encoding method.
Figure 5 shows an example of an intra prediction-based video/image encoding method.
Figure 6 exemplarily shows an intra prediction procedure.
Figure 7 shows an example in which cu_qp_delta for TUs in a CU of 128x128 size is transmitted.
Figure 8 shows an example of a QP map for a luma block and a chroma block when a single tree is used.
Figure 9 shows an example of a QP map for a chroma block when a dual tree is used.
Figure 10 exemplarily shows sample positions for deblocking filtering.
Figure 11 schematically shows an image encoding method using an encoding device according to this document.
Figure 12 schematically shows an encoding device that performs the image encoding method according to this document.
Figure 13 schematically shows a video decoding method using a decoding device according to this document.
Figure 14 schematically shows a decoding device that performs the image decoding method according to this document.
Figure 15 exemplarily shows a content streaming system structural diagram to which embodiments of this document are applied.

Since this document can be subject to various changes and can have several embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments of this document to specific embodiments. Terms used in this specification are merely used to describe specific embodiments and are not intended to limit the technical idea of this document. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features or It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Meanwhile, each component in the drawings described in this document is shown independently for the convenience of explanation of different characteristic functions, and does not mean that each component is implemented with separate hardware or separate software. For example, two or more of each configuration may be combined to form one configuration, or one configuration may be divided into a plurality of configurations. Embodiments in which each component is integrated and/or separated are also included in the scope of rights of this document as long as they do not deviate from the essence of this document.

Hereinafter, preferred embodiments of this document will be described in more detail with reference to the attached drawings. Hereinafter, the same reference numerals will be used for the same components in the drawings, and duplicate descriptions for the same components may be omitted.

1 schematically shows an example of a video/image coding system to which embodiments of this document can be applied.

Referring to FIG. 1, a video/image coding system may include a first device (source device) and a second device (receiving device). The source device can transmit encoded video/image information or data in file or streaming form to a receiving device through a digital storage medium or network.

The source device may include a video source, an encoding device, and a transmission unit. The receiving device may include a receiving unit, a decoding device, and a renderer. The encoding device may be called a video/image encoding device, and the decoding device may be called a video/image decoding device. A transmitter may be included in the encoding device. A receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be composed of a separate device or external component.

A video source can acquire video/image through the process of capturing, compositing, or creating video/image. A video source may include a video/image capture device and/or a video/image generation device. A video/image capture device may include, for example, one or more cameras, a video/image archive containing previously captured video/images, etc. Video/image generating devices may include, for example, computers, tablets, and smartphones, and are capable of generating video/images (electronically). For example, a virtual video/image may be created through a computer, etc., and in this case, the video/image capture process may be replaced by the process of generating related data.

The encoding device can encode input video/image. The encoding device can perform a series of procedures such as prediction, transformation, and quantization for compression and coding efficiency. Encoded data (encoded video/image information) may be output in the form of a bitstream.

The transmitting unit may transmit the encoded video/image information or data output in the form of a bitstream to the receiving unit of the receiving device through a digital storage medium or network in the form of a file or streaming. Digital storage media may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmission unit may include elements for creating a media file through a predetermined file format and may include elements for transmission through a broadcasting/communication network. The receiving unit may receive/extract the bitstream and transmit it to the decoding device.

The decoding device can decode the video/image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction that correspond to the operation of the encoding device.

The renderer can render the decoded video/image. The rendered video/image may be displayed through the display unit.

This document is about video/image coding. For example, the methods/embodiments disclosed in this document may be applicable to the versatile video coding (VVC) standard, the essential video coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the 2nd generation of audio video coding standard (AVS2), or the next generation video/ It can be applied to methods disclosed in video coding standards (ex. H.267 or H.268, etc.).

This document presents various embodiments of video/image coding, and unless otherwise specified, the embodiments may be performed in combination with each other.

In this document, video may refer to a series of images over time. A picture generally refers to a unit representing one image at a specific time, and a subpicture/slice/tile is a unit that forms part of a picture in coding. A subpicture/slice/tile may contain one or more coding tree units (CTUs). One picture may consist of one or more subpictures/slices/tiles. One picture may consist of one or more tile groups. One tile group may include one or more tiles. A brick may represent a rectangular region of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, each of which consisting of one or more CTU rows within the tile. ). A tile that is not partitioned into multiple bricks may be also referred to as a brick. A brick scan may represent a specific sequential ordering of the CTUs partitioning a picture, where the CTUs may be aligned within a brick with a CTU raster scan, and the bricks within a tile may be sequentially aligned with a raster scan of the bricks of the tile. A brick scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a brick , bricks within a tile are ordered consecutively in a raster scan of the bricks of the tile, and tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture). Additionally, a subpicture may represent a rectangular region of one or more slices within a picture. That is, a subpicture may include one or more slices that collectively cover a rectangular region of a picture. A tile is a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. The tile column is a rectangular region of CTUs, the rectangular region has a height equal to the height of the picture, and the width can be specified by syntax elements in the picture parameter set (The tile column is a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements in the picture parameter set). The tile row is a rectangular region of CTUs, and the rectangular region has a width specified by syntax elements in a picture parameter set, and a height may be equal to the height of the picture (The tile row is a rectangular region of CTUs having a height specified by syntax elements in the picture parameter set and a width equal to the width of the picture). A tile scan may represent a specific sequential ordering of CTUs partitioning a picture, where the CTUs may be sequentially aligned with a CTU raster scan within a tile, and tiles within a picture may be sequentially aligned with a raster scan of the tiles in the picture. (A tile scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture). A slice may include an integer number of bricks of a picture, and the integer number of bricks may be contained in one NAL unit (A slice includes an integer number of bricks of a picture that may be exclusively contained in a single NAL unit). A slice may consist of either a number of complete tiles or only a consecutive sequence of complete bricks of one tile ). In this document, tile group and slice may be used interchangeably. For example, in this document, tile group/tile group header may be called slice/slice header.

A pixel or pel may refer to the minimum unit that constitutes one picture (or video). Additionally, 'sample' may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel/pixel value of a luma component, or only a pixel/pixel value of a chroma component.

A unit may represent the basic unit of image processing. A unit may include at least one of a specific area of a picture and information related to the area. One unit may include one luma block and two chroma (ex. cb, cr) blocks. In some cases, unit may be used interchangeably with terms such as block or area. In a general case, an MxN block may include a set (or array) of samples (or a sample array) or transform coefficients consisting of M columns and N rows.

As used herein, “A or B” may mean “only A,” “only B,” or “both A and B.” In other words, as used herein, “A or B” may be interpreted as “A and/or B.” For example, as used herein, “A, B or C” refers to “only A,” “only B,” “only C,” or “any and all combinations of A, B, and C ( It can mean “any combination of A, B and C)”.

The slash (/) or comma used in this specification may mean “and/or.” For example, “A/B” can mean “A and/or B.” Accordingly, “A/B” can mean “only A,” “only B,” or “both A and B.” For example, “A, B, C” can mean “A, B, or C.”

As used herein, “at least one of A and B” may mean “only A,” “only B,” or “both A and B.” In addition, in this specification, the expression "at least one of A or B" or "at least one of A and/or B" means "at least one It can be interpreted the same as "at least one of A and B".

Additionally, as used herein, “at least one of A, B and C” means “only A”, “only B”, “only C”, or “A, B and C”. It can mean “any combination of A, B and C.” Also, “at least one of A, B or C” or “at least one of A, B and/or C” means It may mean “at least one of A, B and C.”

Additionally, parentheses used in this specification may mean “for example.” Specifically, when “prediction (intra prediction)” is indicated, “intra prediction” may be proposed as an example of “prediction.” In other words, “prediction” in this specification is not limited to “intra prediction,” and “intra prediction” may be proposed as an example of “prediction.” Additionally, even when “prediction (i.e., intra prediction)” is indicated, “intra prediction” may be suggested as an example of “prediction.”

Technical features described individually in one drawing in this specification may be implemented individually or simultaneously.

The following drawings were prepared to explain a specific example of the present specification. Since the names of specific devices or specific signals/messages/fields described in the drawings are provided as examples, the technical features of this specification are not limited to the specific names used in the drawings below.

Figure 2 is a diagram schematically explaining the configuration of a video/image encoding device to which embodiments of this document can be applied. Hereinafter, the video encoding device may include a video encoding device.

Referring to FIG. 2, the encoding device 200 includes an image partitioner (210), a predictor (220), a residual processor (230), an entropy encoder (240), It may be configured to include an adder (250), a filter (260), and a memory (270). The prediction unit 220 may include an inter prediction unit 221 and an intra prediction unit 222. The residual processing unit 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processing unit 230 may further include a subtractor 231. The adder 250 may be called a reconstructor or a reconstructed block generator. The above-described image segmentation unit 210, prediction unit 220, residual processing unit 230, entropy encoding unit 240, addition unit 250, and filtering unit 260 may include one or more hardware components (depending on the embodiment). For example, it may be configured by an encoder chipset or processor). Additionally, the memory 270 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may further include a memory 270 as an internal/external component.

The image segmentation unit 210 may divide an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit may be called a coding unit (CU). In this case, the coding unit will be split recursively according to the QTBTTT (Quad-tree binary-tree ternary-tree) structure from the coding tree unit (CTU) or the largest coding unit (LCU). You can. For example, one coding unit may be divided into a plurality of coding units of deeper depth based on a quad tree structure, binary tree structure, and/or ternary structure. In this case, for example, the quad tree structure may be applied first and the binary tree structure and/or ternary structure may be applied later. Alternatively, the binary tree structure may be applied first. The coding procedure according to this document can be performed based on the final coding unit that is no longer divided. In this case, based on coding efficiency according to video characteristics, the largest coding unit can be used directly as the final coding unit, or, if necessary, the coding unit is recursively divided into coding units of lower depth to determine the optimal coding unit. A coding unit of size may be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may each be divided or partitioned from the final coding unit described above. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving a transform coefficient and/or a unit for deriving a residual signal from the transform coefficient.

In some cases, unit may be used interchangeably with terms such as block or area. In a general case, an MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a pixel value, and may represent only a pixel/pixel value of a luminance (luma) component, or only a pixel/pixel value of a chroma component. A sample may be used as a term that corresponds to a pixel or pel of one picture (or video).

The encoding device 200 subtracts the prediction signal (predicted block, prediction sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from the input image signal (original block, original sample array) to generate the residual. A signal (residual block, residual sample array) can be generated, and the generated residual signal is transmitted to the converter 232. In this case, as shown, the unit that subtracts the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) within the encoder 200 may be called the subtraction unit 231. The prediction unit may perform prediction on a block to be processed (hereinafter referred to as a current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied on a current block or CU basis. As will be described later in the description of each prediction mode, the prediction unit may generate various information related to prediction, such as prediction mode information, and transmit it to the entropy encoding unit 240. Information about prediction may be encoded in the entropy encoding unit 240 and output in the form of a bitstream.

The intra prediction unit 222 can predict the current block by referring to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from the current block depending on the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. Non-directional modes may include, for example, DC mode and planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the level of detail of the prediction direction. However, this is an example and more or less directional prediction modes may be used depending on the setting. The intra prediction unit 222 may determine the prediction mode applied to the current block using the prediction mode applied to the neighboring block.

The inter prediction unit 221 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector in the reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted on a block, subblock, or sample basis based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, neighboring blocks may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. A reference picture including the reference block and a reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a collocated reference block, a collocated CU (colCU), etc., and a reference picture including the temporal neighboring block may be called a collocated picture (colPic). It may be possible. For example, the inter prediction unit 221 constructs a motion information candidate list based on neighboring blocks and provides information indicating which candidate is used to derive the motion vector and/or reference picture index of the current block. can be created. Inter prediction may be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter prediction unit 221 may use motion information of neighboring blocks as motion information of the current block. In the case of skip mode, unlike merge mode, residual signals may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the surrounding block is used as a motion vector predictor, and the motion vector of the current block is predicted by signaling the motion vector difference. You can instruct.

The prediction unit 220 may generate a prediction signal based on various prediction methods described later. For example, the prediction unit can not only apply intra prediction or inter prediction for prediction of one block, but also can apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). Additionally, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode for prediction of a block. The IBC prediction mode or palette mode can be used, for example, for video/video coding of content such as games, such as screen content coding (SCC). IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC can use at least one of the inter prediction techniques described in this document. Palette mode can be viewed as an example of intra coding or intra prediction. When palette mode is applied, sample values within a picture can be signaled based on information about the palette table and palette index.

The prediction signal generated through the prediction unit (including the inter prediction unit 221 and/or the intra prediction unit 222) may be used to generate a restored signal or a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transformation technique may be at least one of Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), Karhunen-Loeve Transform (KLT), Graph-Based Transform (GBT), or Conditionally Non-linear Transform (CNT). It can be included. Here, GBT refers to the transformation obtained from this graph when the relationship information between pixels is expressed as a graph. CNT refers to the transformation obtained by generating a prediction signal using all previously reconstructed pixels and obtaining it based on it. Additionally, the conversion process may be applied to square pixel blocks of the same size, or to non-square blocks of variable size.

The quantization unit 233 quantizes the transform coefficients and transmits them to the entropy encoding unit 240, and the entropy encoding unit 240 encodes the quantized signal (information about the quantized transform coefficients) and outputs it as a bitstream. there is. Information about the quantized transform coefficients may be called residual information. The quantization unit 233 may rearrange the quantized transform coefficients in block form into a one-dimensional vector form based on the coefficient scan order, and the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. Information about transformation coefficients may also be generated. The entropy encoding unit 240 may perform various encoding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 240 may encode information necessary for video/image restoration (e.g., values of syntax elements, etc.) in addition to the quantized transformation coefficients together or separately. Encoded information (ex. encoded video/picture information) may be transmitted or stored in bitstream form in units of NAL (network abstraction layer) units. The video/image information may further include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Additionally, the video/image information may further include general constraint information. In this document, information and/or syntax elements transmitted/signaled from an encoding device to a decoding device may be included in video/image information. The video/image information may be encoded through the above-described encoding procedure and included in the bitstream. The bitstream can be transmitted over a network or stored in a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The signal output from the entropy encoding unit 240 may be configured as an internal/external element of the encoding device 200 by a transmission unit (not shown) for transmitting and/or a storage unit (not shown) for storing the signal. It may also be included in the entropy encoding unit 240.

Quantized transform coefficients output from the quantization unit 233 can be used to generate a prediction signal. For example, a residual signal (residual block or residual samples) can be restored by applying inverse quantization and inverse transformation to the quantized transformation coefficients through the inverse quantization unit 234 and the inverse transformation unit 235. The adder 250 adds the reconstructed residual signal to the prediction signal output from the inter prediction unit 221 or the intra prediction unit 222, thereby creating a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). can be created. If there is no residual for the block to be processed, such as when skip mode is applied, the predicted block can be used as a restoration block. The addition unit 250 may be called a restoration unit or a restoration block generation unit. The generated reconstructed signal can be used for intra prediction of the next processing target block in the current picture, and can also be used for inter prediction of the next picture after filtering, as will be described later.

Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and/or restoration process.

The filtering unit 260 can improve subjective/objective image quality by applying filtering to the restored signal. For example, the filtering unit 260 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 270, specifically the DPB of the memory 270. It can be saved in . The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filtering unit 260 may generate various information regarding filtering and transmit it to the entropy encoding unit 240, as will be described later in the description of each filtering method. Information about filtering may be encoded in the entropy encoding unit 240 and output in the form of a bitstream.

The modified reconstructed picture transmitted to the memory 270 can be used as a reference picture in the inter prediction unit 221. Through this, the encoding device can avoid prediction mismatch in the encoding device 200 and the decoding device 300 when inter prediction is applied, and can also improve encoding efficiency.

The memory 270 DPB can store the modified reconstructed picture to use it as a reference picture in the inter prediction unit 221. The memory 270 may store motion information of a block from which motion information in the current picture is derived (or encoded) and/or motion information of blocks in an already reconstructed picture. The stored motion information can be transmitted to the inter prediction unit 221 to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks. The memory 270 can store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra prediction unit 222.

Figure 3 is a diagram schematically explaining the configuration of a video/image decoding device to which embodiments of this document can be applied.

Referring to FIG. 3, the decoding device 300 includes an entropy decoder (310), a residual processor (320), a predictor (330), an adder (340), and a filtering unit. It may be configured to include (filter, 350) and memory (memory, 360). The prediction unit 330 may include an inter prediction unit 331 and an intra prediction unit 332. The residual processing unit 320 may include a dequantizer (321) and an inverse transformer (322). Depending on the embodiment, the entropy decoding unit 310, residual processing unit 320, prediction unit 330, addition unit 340, and filtering unit 350 may be comprised of one hardware component (e.g., a decoder chipset or processor). ) can be configured by. Additionally, the memory 360 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may further include a memory 360 as an internal/external component.

When a bitstream including video/image information is input, the decoding device 300 may restore the image in response to the process in which the video/image information is processed in the encoding device of FIG. 2. For example, the decoding device 300 may derive units/blocks based on block division-related information obtained from the bitstream. The decoding device 300 may perform decoding using a processing unit applied in the encoding device. Accordingly, the processing unit of decoding may for example be a coding unit, and the coding unit may be split along a quad tree structure, a binary tree structure and/or a ternary tree structure from a coding tree unit or a maximum coding unit. One or more transformation units can be derived from a coding unit. And, the restored video signal decoded and output through the decoding device 300 can be played through a playback device.

The decoding device 300 may receive the signal output from the encoding device of FIG. 2 in the form of a bitstream, and the received signal may be decoded through the entropy decoding unit 310. For example, the entropy decoder 310 may parse the bitstream to derive information (ex. video/picture information) necessary for image restoration (or picture restoration). The video/image information may further include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Additionally, the video/image information may further include general constraint information. The decoding device may decode a picture further based on information about the parameter set and/or the general restriction information. Signaled/received information and/or syntax elements described later in this document may be decoded through the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 decodes information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and quantizes the value of the syntax element required for image restoration and the quantized value of the transform coefficient for the residual. can be printed out. In more detail, the CABAC entropy decoding method receives bins corresponding to each syntax element from the bitstream, and provides syntax element information to be decoded, decoding information of surrounding and target blocks to be decoded, or information of symbols/bins decoded in the previous step. You can use this to determine a context model, predict the probability of occurrence of a bin according to the determined context model, perform arithmetic decoding of the bin, and generate symbols corresponding to the value of each syntax element. there is. At this time, the CABAC entropy decoding method can update the context model using information on the decoded symbol/bin for the context model of the next symbol/bin after determining the context model. Among the information decoded in the entropy decoding unit 310, information about prediction is provided to the prediction unit (inter prediction unit 332 and intra prediction unit 331), and the register on which entropy decoding was performed in the entropy decoding unit 310 Dual values, that is, quantized transform coefficients and related parameter information, may be input to the residual processing unit 320. The residual processing unit 320 may derive a residual signal (residual block, residual samples, residual sample array). Additionally, information about filtering among the information decoded by the entropy decoding unit 310 may be provided to the filtering unit 350. Meanwhile, a receiving unit (not shown) that receives the signal output from the encoding device may be further configured as an internal/external element of the decoding device 300, or the receiving unit may be a component of the entropy decoding unit 310. Meanwhile, the decoding device according to this document may be called a video/image/picture decoding device, and the decoding device can be divided into an information decoder (video/image/picture information decoder) and a sample decoder (video/image/picture sample decoder). It may be possible. The information decoder may include the entropy decoding unit 310, and the sample decoder may include the inverse quantization unit 321, the inverse transform unit 322, the addition unit 340, the filtering unit 350, and the memory 360. ), it may include at least one of the inter prediction unit 332 and the intra prediction unit 331.

The inverse quantization unit 321 may inversely quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit 321 may rearrange the quantized transform coefficients into a two-dimensional block form. In this case, the reordering may be performed based on the coefficient scan order performed in the encoding device. The inverse quantization unit 321 may perform inverse quantization on quantized transform coefficients using quantization parameters (eg, quantization step size information) and obtain transform coefficients.

The inverse transform unit 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

The prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the information about the prediction output from the entropy decoding unit 310, and may determine a specific intra/inter prediction mode.

The prediction unit 320 may generate a prediction signal based on various prediction methods described later. For example, the prediction unit can not only apply intra prediction or inter prediction for prediction of one block, but also can apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). Additionally, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode for prediction of a block. The IBC prediction mode or palette mode can be used, for example, for video/video coding of content such as games, such as screen content coding (SCC). IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC can use at least one of the inter prediction techniques described in this document. Palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, information about the palette table and palette index may be signaled and included in the video/image information.

The intra prediction unit 331 can predict the current block by referring to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from the current block depending on the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may determine the prediction mode applied to the current block using the prediction mode applied to the neighboring block.

The inter prediction unit 332 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector in the reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted on a block, subblock, or sample basis based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, neighboring blocks may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. For example, the inter prediction unit 332 may construct a motion information candidate list based on neighboring blocks and derive a motion vector and/or reference picture index of the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the information about the prediction may include information indicating the mode of inter prediction for the current block.

The adder 340 restores the obtained residual signal by adding it to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit 332 and/or the intra prediction unit 331). A signal (restored picture, restored block, restored sample array) can be generated. If there is no residual for the block to be processed, such as when skip mode is applied, the predicted block can be used as a restoration block.

The addition unit 340 may be called a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, may be output after filtering as described later, or may be used for inter prediction of the next picture.

Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture decoding process.

The filtering unit 350 can improve subjective/objective image quality by applying filtering to the restored signal. For example, the filtering unit 350 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 360, specifically the DPB of the memory 360. can be transmitted to. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

The (corrected) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter prediction unit 332. The memory 360 may store motion information of a block from which motion information in the current picture is derived (or decoded) and/or motion information of blocks in a picture that has already been reconstructed. The stored motion information can be transmitted to the inter prediction unit 260 to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks. The memory 360 can store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra prediction unit 331.

In this specification, the embodiments described in the filtering unit 260, the inter prediction unit 221, and the intra prediction unit 222 of the encoding device 200 are the filtering unit 350 and the inter prediction unit of the decoding device 300, respectively. The same or corresponding application may be applied to the unit 332 and the intra prediction unit 331.

In this document, at least one of quantization/dequantization and/or transformation/inverse transformation may be omitted. If the quantization/dequantization is omitted, the quantized transform coefficient may be called a transform coefficient. If the transform/inverse transform is omitted, the transform coefficient may be called a coefficient or residual coefficient, or may still be called a transform coefficient for unity of expression.

In this document, quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information may include information about the transform coefficient(s), and the information about the transform coefficient(s) can be signaled through residual coding syntax. Transform coefficients can be derived based on the residual information (or information about the transform coefficient(s)), and scaled transform coefficients can be derived through inverse transformation (scaling) of the transform coefficients. Residual samples may be derived based on inverse transformation (transformation) of the scaled transformation coefficients. This can be similarly applied/expressed in other parts of this document.

As described above, when performing video coding, prediction is performed to increase compression efficiency. Through this, a predicted block containing prediction samples for the current block, which is the coding target block, can be generated. Here, the predicted block includes prediction samples in the spatial domain (or pixel domain). The predicted block is derived equally from the encoding device and the decoding device, and the encoding device decodes information about the residual between the original block and the predicted block (residual information) rather than the original sample value of the original block itself. Video coding efficiency can be increased by signaling to the device. The decoding device may derive a residual block including residual samples based on the residual information, generate a restored block including restored samples by combining the residual block and the predicted block, and generate the restored blocks. A restored picture containing the image can be generated.

The residual information can be generated through transformation and quantization procedures. For example, the encoding device derives a residual block between the original block and the predicted block, and performs a transformation procedure on residual samples (residual sample array) included in the residual block to derive transformation coefficients. Then, a quantization procedure can be performed on the transform coefficients to derive quantized transform coefficients, and the related residual information can be signaled to the decoding device (via a bitstream). Here, the residual information may include information such as value information of the quantized transform coefficients, position information, transform technique, transform kernel, and quantization parameters. The decoding device may perform an inverse quantization/inverse transformation procedure based on the residual information and derive residual samples (or residual blocks). The decoding device can generate a restored picture based on the predicted block and the residual block. The encoding device may also dequantize/inverse transform the quantized transform coefficients to derive a residual block for reference for inter prediction of a subsequent picture, and generate a restored picture based on this.

Intra prediction may refer to prediction that generates prediction samples for the current block based on reference samples within the picture to which the current block belongs (hereinafter, current picture). When intra prediction is applied to the current block, surrounding reference samples to be used for intra prediction of the current block may be derived. The surrounding reference samples of the current block include samples adjacent to the left border of the current block of size nWxnH, a total of 2xnH samples neighboring the bottom-left, and samples adjacent to the top border of the current block. And it may include a total of 2xnW samples neighboring the top-right and one sample neighboring the top-left of the current block. Alternatively, the peripheral reference samples of the current block may include multiple rows of upper peripheral samples and multiple rows of left peripheral samples. In addition, the surrounding reference samples of the current block include a total of nH samples adjacent to the right border of the current block of size nWxnH, a total of nW samples adjacent to the bottom border of the current block, and a total of nW samples adjacent to the bottom border of the current block. It may also include one sample neighboring (bottom-right).

However, some of the surrounding reference samples of the current block may not have been decoded yet or may not be available. In this case, the decoder can construct surrounding reference samples to be used for prediction by substituting unavailable samples with available samples. Alternatively, surrounding reference samples to be used for prediction can be configured through interpolation of available samples.

When neighboring reference samples are derived, (i) a prediction sample can be derived based on the average or interpolation of the neighboring reference samples of the current block, and (ii) the neighboring reference sample of the current block Among these, the prediction sample may be derived based on a reference sample that exists in a specific (prediction) direction with respect to the prediction sample. In case (i), it can be called a non-directional mode or non-angular mode, and in case (ii), it can be called a directional mode or angular mode.

In addition, among the surrounding reference samples, a first surrounding sample located in the prediction direction of the intra prediction mode of the current block based on the prediction sample of the current block and a second surrounding sample located in the opposite direction of the prediction direction are used. The prediction sample may be generated through interpolation. The above-described case may be called linear interpolation intra prediction (LIP). Additionally, chroma prediction samples may be generated based on luma samples using a linear model (LM). This case may be called LM mode or CCLM (chroma component LM) mode.

In addition, a temporary prediction sample of the current block is derived based on filtered neighboring reference samples, and at least one derived according to the intra prediction mode among the existing neighboring reference samples, that is, unfiltered neighboring reference samples The prediction sample of the current block may be derived by performing a weighted sum of the reference sample and the temporary prediction sample. The above-described case may be called PDPC (Position dependent intra prediction).

In addition, the reference sample line with the highest prediction accuracy among the surrounding multiple reference sample lines of the current block is selected to derive a prediction sample using the reference sample located in the prediction direction from that line, and at this time, the used reference sample line is decoded. Intra prediction encoding can be performed by instructing (signaling) the device. The above-described case may be called multi-reference line intra prediction or MRL-based intra prediction.

In addition, intra prediction can be performed based on the same intra prediction mode by dividing the current block into vertical or horizontal subpartitions, and surrounding reference samples can be derived and used in units of the subpartitions. That is, in this case, the intra prediction mode for the current block is equally applied to the subpartitions, but intra prediction performance can be improved in some cases by deriving and using surrounding reference samples for each subpartition. This prediction method may be called ISP (intra sub-partitions) based intra prediction.

The above-described intra prediction methods may be called an intra prediction type, distinguishing them from the intra prediction mode. The intra prediction type may be called various terms such as intra prediction technique or additional intra prediction mode. For example, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the above-described LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP may be called a normal intra prediction type. The normal intra prediction type can be generally applied when the specific intra prediction type as described above is not applied, and prediction can be performed based on the intra prediction mode described above. Meanwhile, post-processing filtering may be performed on the derived prediction samples as needed.

Specifically, the intra prediction procedure may include an intra prediction mode/type determination step, a peripheral reference sample derivation step, and an intra prediction mode/type-based prediction sample derivation step. Additionally, a post-filtering step may be performed on the derived prediction sample as needed.

Figure 4 shows an example of an intra prediction-based video/image encoding method.

Referring to FIG. 4, the encoding device performs intra prediction on the current block (S400). The encoding device may derive an intra prediction mode/type for the current block, derive surrounding reference samples of the current block, and generate prediction samples within the current block based on the intra prediction mode/type and the surrounding reference samples. do. Here, the procedures for determining intra prediction mode/type, deriving peripheral reference samples, and generating prediction samples may be performed simultaneously, or one procedure may be performed before the other procedure. The encoding device may determine a mode/type applied to the current block among a plurality of intra prediction modes/types. The encoding device may compare RD costs for the intra prediction modes/types and determine the optimal intra prediction mode/type for the current block.

Meanwhile, the encoding device may perform a prediction sample filtering procedure. Predictive sample filtering can be called post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

The encoding device generates residual samples for the current block based on (filtered) prediction samples (S410). The encoding device may compare the prediction samples with the original samples of the current block based on phase and derive the residual samples.

The encoding device may encode image information including information about the intra prediction (prediction information) and residual information about the residual samples (S420). The prediction information may include the intra prediction mode information and the intra prediction type information. The encoding device may output encoded video information in the form of a bitstream. The output bitstream may be transmitted to a decoding device through a storage medium or network.

The residual information may include residual coding syntax, which will be described later. The encoding device can transform/quantize the residual samples to derive quantized transform coefficients. The residual information may include information about the quantized transform coefficients.

Meanwhile, as described above, the encoding device can generate a reconstructed picture (including reconstructed samples and a reconstructed block). To this end, the encoding device can dequantize/inverse transform the quantized transform coefficients again to derive (corrected) residual samples. The reason for performing inverse quantization/inverse transformation again after transforming/quantizing the residual samples is to derive residual samples that are identical to the residual samples derived from the decoding device, as described above. The encoding device may generate a restored block including restored samples for the current block based on the prediction samples and the (corrected) residual samples. A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering procedure, etc. may be further applied to the reconstructed picture.

Figure 5 shows an example of an intra prediction-based video/image encoding method.

The decoding device may perform an operation corresponding to the operation performed by the encoding device.

Prediction information and residual information can be obtained from the bitstream. Based on the residual information, residual samples for the current block can be derived. Specifically, based on the quantized transform coefficients derived based on the residual information, transform coefficients are derived by performing inverse quantization, and inverse transform is performed on the transform coefficients to derive residual samples for the current block. can do.

Specifically, the decoding device may derive the intra prediction mode/type for the current block based on the received prediction information (intra prediction mode/type information) (S500). The decoding device may derive surrounding reference samples of the current block (S510). The decoding device generates prediction samples within the current block based on the intra prediction mode/type and the surrounding reference samples (S520). In this case, the decoding device may perform a predictive sample filtering procedure. Predictive sample filtering can be called post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

The decoding device generates residual samples for the current block based on the received residual information (S530). The decoding device may generate restored samples for the current block based on the prediction samples and the residual samples and derive a restored block including the restored samples (S540). A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering procedure, etc. may be further applied to the reconstructed picture.

The intra prediction mode information may include, for example, flag information (ex. intra_luma_mpm_flag) indicating whether MPM (most probable mode) or retaining mode is applied to the current block, When MPM is applied to the current block, the prediction mode information may further include index information (ex. intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list. In addition, when the MPM is not applied to the current block, the intra prediction mode information includes reminding mode information (ex. intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates). More may be included. The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

Additionally, the intra prediction type information may be implemented in various forms. As an example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information includes reference sample line information (ex. intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if applied, which reference sample line is used, and the ISP determines whether the current block It may include at least one of ISP flag information (ex. intra_subpartitions_mode_flag) indicating whether the ISP is applied or ISP type information (ex. intra_subpartitions_split_flag) indicating the split type of subpartitions when the ISP is applied. Additionally, the intra prediction type information may include an MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

The intra prediction mode information and/or the intra prediction type information may be encoded/decoded through the coding method described in this document. For example, the intra prediction mode information and/or the intra prediction type information may be encoded/decoded through entropy coding (ex. CABAC, CAVLC) coding.

Figure 6 exemplarily shows an intra prediction procedure.

Referring to FIG. 6, as described above, the intra prediction procedure may include an intra prediction mode/type determination step, a peripheral reference sample derivation step, and an intra prediction performance (prediction sample generation) step. The intra prediction procedure may be performed in the encoding device and the decoding device as described above. In this document, a coding device may include an encoding device and/or a decoding device.

Referring to FIG. 6, the coding device determines the intra prediction mode/type (S600).

The encoding device can determine the intra prediction mode/type applied to the current block among the various intra prediction modes/types described above and generate prediction-related information. The prediction-related information may include intra prediction mode information indicating an intra prediction mode applied to the current block and/or intra Yes type information indicating an intra prediction type applied to the current block. The decoding device may determine the intra prediction mode/type applied to the current block based on the prediction-related information.

The intra prediction mode information may include, for example, flag information (ex. intra_luma_mpm_flag) indicating whether MPM (most probable mode) or retaining mode is applied to the current block, When MPM is applied to the current block, the prediction mode information may further include index information (ex. intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list. In addition, when the MPM is not applied to the current block, the intra prediction mode information includes reminding mode information (ex. intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates). More may be included. The decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

Additionally, the intra prediction type information may be implemented in various forms. As an example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information includes reference sample line information (ex. intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if applied, which reference sample line is used, and the ISP determines whether the current block It may include at least one of ISP flag information (ex. intra_subpartitions_mode_flag) indicating whether the ISP is applied or ISP type information (ex. intra_subpartitions_split_flag) indicating the split type of subpartitions when the ISP is applied. Additionally, the intra prediction type information may include an MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

For example, when intra prediction is applied, the intra prediction mode applied to the current block may be determined using the intra prediction mode of the neighboring block. For example, the coding device may select one of the MPM candidates in the most probable mode (MPM) list derived based on the intra prediction mode and/or additional candidate modes of the neighboring block (e.g., left and/or upper neighboring blocks) of the current block. can be selected based on the received MPM index, or one of the remaining intra prediction modes not included in the MPM candidates (and planner mode) can be selected based on MPM reminder information (remaining intra prediction mode information). You can. The MPM list may be configured to include or not include the planner mode as a candidate. For example, if the MPM list includes the planner mode as a candidate, the MPM list may have 6 candidates, and if the MPM list does not include the planner mode as a candidate, the MPM list may have 5 candidates. You can. If the MPM list does not include a planner mode as a candidate, a not planner flag (ex. intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not a planner mode may be signaled. For example, the MPM flag may be signaled first, and the MPM index and not planner flag may be signaled when the value of the MPM flag is 1. Additionally, the MPM index may be signaled when the value of the not planner flag is 1. Here, the fact that the MPM list is configured not to include the planner mode as a candidate does not mean that the planner mode is not an MPM, but rather that the planner mode is always considered as an MPM, so a flag (not planar flag) is signaled first to select the planner mode. This is to first check whether it is recognized or not.

For example, whether the intra prediction mode applied to the current block is among MPM candidates (and planner mode) or remaining mode may be indicated based on the MPM flag (ex. intra_luma_mpm_flag). A value of 1 in the MPM flag may indicate that the intra prediction mode for the current block is within the MPM candidates (and planner mode), and a value of 0 in the MPM flag may indicate that the intra prediction mode for the current block is within the MPM candidates (and planner mode). ) can indicate that it is not within. The not planar flag (ex. intra_luma_not_planar_flag) value of 0 may indicate that the intra prediction mode for the current block is the planar mode, and the not planar flag value of 1 may indicate that the intra prediction mode for the current block is not the planar mode. You can. The MPM index may be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information may be signaled in the form of a rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information may index the remaining intra prediction modes not included in the MPM candidates (and planner mode) among all intra prediction modes in order of prediction mode number and may indicate one of them. The intra prediction mode may be an intra prediction mode for the luma component (sample). Hereinafter, the intra prediction mode information includes at least one of the MPM flag (ex. intra_luma_mpm_flag), the not planar flag (ex. intra_luma_not_planar_flag), the MPM index (ex. mpm_idx or intra_luma_mpm_idx), and the remaking intra prediction mode information (rem_intra_luma_pred_mode or intra_luma_mpm_remainder). may include. In this document, the MPM list may be called various terms such as MPM candidate list, candModeList, etc.

When the MIP is applied to the current block, a separate MPM flag (ex. intra_mip_mpm_flag), MPM index (ex. intra_mip_mpm_idx), and remaining intra prediction mode information (ex. intra_mip_mpm_remainder) for the MIP may be signaled, and the not planar flag may not be signaled.

In other words, generally, when an image is divided into blocks, the current block to be coded and neighboring blocks have similar image characteristics. Therefore, there is a high probability that the current block and neighboring blocks have the same or similar intra prediction modes. Accordingly, the encoder can use the intra prediction mode of the neighboring block to encode the intra prediction mode of the current block.

The coding device may construct a list of most probable modes (MPM) for the current block. The MPM list may also be referred to as an MPM candidate list. Here, MPM may refer to a mode used to improve coding efficiency by considering the similarity between the current block and neighboring blocks when coding in intra prediction mode. As described above, the MPM list may be configured to include the planner mode, or may be configured to exclude the planner mode. For example, if the MPM list includes a planner mode, the number of candidates in the MPM list may be 6. And, if the MPM list does not include a planner mode, the number of candidates in the MPM list may be 5.

The encoding device can perform prediction based on various intra prediction modes and determine the optimal intra prediction mode based on rate-distortion optimization (RDO). In this case, the encoding device may determine the optimal intra prediction mode using only the MPM candidates and planner modes configured in the MPM list, or may further use the remaining intra prediction modes as well as the MPM candidates and planner modes configured in the MPM list. The optimal intra prediction mode may be determined. Specifically, for example, if the intra-prediction type of the current block is a specific type (e.g., LIP, MRL, or ISP) rather than the normal intra-prediction type, the encoding device uses only the MPM candidates and planner mode for the current block. The optimal intra prediction mode can be determined by considering the intra prediction mode candidates for . That is, in this case, the intra prediction mode for the current block can be determined only among the MPM candidates and planner modes, and in this case, the MPM flag may not be encoded/signaled. In this case, the decoding device can estimate that the MPM flag is 1 without receiving separate signaling of the MPM flag.

Meanwhile, in general, when the intra prediction mode of the current block is not a planner mode and is one of the MPM candidates in the MPM list, the encoding device generates an MPM index (mpm idx) indicating one of the MPM candidates. If the intra prediction mode of the current block is not even in the MPM list, an MPM list indicating the same mode as the intra prediction mode of the current block among the remaining intra prediction modes not included in the MPM list (and planner mode) Generate main information (remaining intra prediction mode information). The MPM reminder information may include, for example, an intra_luma_mpm_remainder syntax element.

The decoding device obtains intra prediction mode information from the bitstream. As described above, the intra prediction mode information may include at least one of an MPM flag, a not planner flag, an MPM index, and MPM reminder information (remaining intra prediction mode information). The decoding device may construct an MPM list. The MPM list is configured identically to the MPM list configured in the encoding device. That is, the MPM list may include intra prediction modes of neighboring blocks, and may further include specific intra prediction modes according to a predetermined method.

The decoding device may determine the intra prediction mode of the current block based on the MPM list and the intra prediction mode information. For example, when the value of the MPM flag is 1, the decoding device derives the planar mode as the intra prediction mode of the current block (based on the not planar flag) or selects the candidate indicated by the MPM index among the MPM candidates in the MPM list. It can be derived from the intra prediction mode of the current block. Here, MPM candidates may represent only candidates included in the MPM list, or may include not only candidates included in the MPM list but also a planner mode that can be applied when the value of the MPM flag is 1.

As another example, when the value of the MPM flag is 0, the decoding device selects the remaining intra prediction mode information (which may be called mpm remainder information) indicated among the remaining intra prediction modes not included in the MPM list and planner mode. The intra prediction mode can be derived as the intra prediction mode of the current block. Meanwhile, as another example, when the intra prediction type of the current block is a specific type (ex. LIP, MRL, or ISP, etc.), the decoding device operates in the planner mode or the MPM list without parsing/decoding/checking the MPM flag. The candidate indicated by the MPM flag may be derived as the intra prediction mode of the current block.

The coding device derives surrounding reference samples of the current block (S610). When intra prediction is applied to the current block, surrounding reference samples to be used for intra prediction of the current block may be derived. The surrounding reference samples of the current block include samples adjacent to the left border of the current block of size nWxnH, a total of 2xnH samples neighboring the bottom-left, and samples adjacent to the top border of the current block. And it may include a total of 2xnW samples neighboring the top-right and one sample neighboring the top-left of the current block. Alternatively, the peripheral reference samples of the current block may include multiple rows of upper peripheral samples and multiple rows of left peripheral samples. In addition, the surrounding reference samples of the current block include a total of nH samples adjacent to the right border of the current block of size nWxnH, a total of nW samples adjacent to the bottom border of the current block, and a total of nW samples adjacent to the bottom border of the current block. It may also include one sample neighboring (bottom-right).

Meanwhile, when MRL is applied (i.e., when the value of the MRL index is greater than 0), the surrounding reference samples may be located on lines 1 and 2, rather than line 0 adjacent to the current block on the left/top side. And in this case, the number of surrounding reference samples can be further increased. Meanwhile, when ISP is applied, the surrounding reference samples can be derived on a subpartition basis.

The coding device performs intra prediction on the current block to derive prediction samples (S620). The coding device may derive the prediction samples based on the intra prediction mode/type and the surrounding samples. The coding device may derive a reference sample according to the intra prediction mode of the current block among the surrounding reference samples of the current block, and may derive a prediction sample of the current block based on the reference sample.

Meanwhile, as described above, the quantizer of the encoding device may apply quantization to the transform coefficients to derive quantized transform coefficients, and the inverse quantizer of the encoding device or the inverse quantizer of the decoding device may inversely quantize the quantized transform coefficients. Transformation coefficients can be derived by applying .

In general, in video/image coding, the quantization rate can be changed, and compression can be adjusted using the changed quantization rate. From an implementation perspective, considering complexity, a quantization parameter (QP) can be used instead of using the quantization rate directly. For example, quantization parameters with integer values from 0 to 63 may be used, and each quantization parameter value may correspond to an actual quantization rate. Additionally, for example, the quantization parameter (QP _Y ) for the luma component (luma sample) and the quantization parameter (QP _C ) for the chroma component (chroma sample) may be set differently.

The quantization process takes the transformation coefficient (C) as input, divides it by the quantization rate (Q _step ), and obtains the quantized transformation coefficient (C') based on this. In this case, considering calculation complexity, the quantization rate can be multiplied by the scale to form an integer, and a shift operation can be performed by a value corresponding to the scale value. A quantization scale can be derived based on the product of the quantization rate and the scale value. That is, the quantization scale can be derived according to QP. For example, the quantization scale may be applied to the transform coefficient (C), and a quantized transform coefficient (C′) may be derived based on this.

The inverse quantization process is the reverse of the quantization process, and the quantized transform coefficient (C`) is multiplied by the quantization rate (Q <sub>step</sub> ), and the restored transform coefficient (C``) can be obtained based on this. In this case, a level scale can be derived according to the quantization parameter, and the level scale is applied to the quantized transform coefficient (C`), and the restored transform coefficient (C``) is derived based on this. It can be. The restored transform coefficient (C``) may be somewhat different from the original transform coefficient (C``) due to loss in the transformation and/or quantization process. Therefore, the encoding device also performs dequantization in the same way as the decoding device.

Meanwhile, adaptive frequency weighting quantization technology that adjusts the quantization strength according to frequency can be applied. The adaptive weighted quantization technology for each frequency is a method of applying different quantization strengths for each frequency. The adaptive weighted quantization for each frequency can apply different quantization strengths for each frequency using a predefined quantization scaling matrix. That is, the above-described quantization/dequantization process can be performed based on the quantization scaling matrix. For example, to generate the size of the current block and/or the residual signal of the current block, different quantization scaling metrics may be used depending on whether the prediction mode applied to the current block is inter prediction or intra prediction. The quantization scaling matrix may be called a quantization matrix or scaling matrix. The quantization scaling matrix may be predefined. Additionally, for frequency adaptive scaling, frequency-specific quantization scale information for the quantization scaling matrix may be configured/encoded in the encoding device and signaled to the decoding device. The quantization scale information for each frequency may be called quantization scaling information. The quantization scale information for each frequency may include scaling list data (scaling_list_data). The (modified) quantization scaling matrix may be derived based on the scaling list data. Additionally, the quantization scale information for each frequency may include present flag information indicating the presence or absence of the scaling list data. Or, when the scaling list data is signaled at a higher level (e.g., SPS), indicates whether the scaling list data is modified at a lower level of the higher level (e.g., PPS or tile group header, etc.) Additional information may be included.

As described above, quantization/dequantization may be applied to the luma component and chroma component based on the quantization parameter.

Meanwhile, in the current video/picture coding standard, for a quantization group, information about the luma QP is signaled as a delta Qp with the previous QP, and transmission of the information may be delayed until the first transform unit with the coded coefficient. there is. Specifically, the syntax element cu_qp_delta representing delta QP may be transmitted in the first transform unit of the quantization group with coded coefficients (i.e., tu_cbf = 1).

Figure 7 shows an example in which cu_qp_delta for TUs in a CU of 128x128 size is transmitted. As shown in FIG. 7, in the case of a large-sized CU, delta QP may not be transmitted until the last TU in coding order. However, the delta QP value transmitted for the last TU can be applied to the entire CU.

Additionally, the concept of 64x64 VDPU (Virtual Decoder Pipeline Unit) can be used in the current video/image coding standard. In particular, the current video/picture coding standard requires maximum transform sizes, structural and syntax elements for luma/chroma syntax interleaving, etc., so that the decoder can use a large size of up to 128x128. The CU can also be designed to process blocks of size 64x64 (i.e., VDPU) at once. Using a 64x64 pipeline can result in significant cost savings in the decoding unit compared to the buffering requirements of a 128x128 pipeline.

However, the Delta QP design in VVC Standard Draft 5 and earlier standards does not fit the 64x64 pipeline concept. Since the QP value is required for in-loop filtering, the absence of the QP value may mean that the process for previous TUs of the CU cannot be completed.

Specifically, the deblocking filter may require a QP to determine filtering thresholds. Therefore, in VVC standard draft 6, a condition was added to delta QP signaling. Specifically, for CUs with cbWidth[chType] > 64 or cbHeight[chType] > 64, signal delta QP regardless of whether the first TU has non-zero coefficients (i.e. coded coefficients). Conditions may be added.

For example, luma delta QP in VVC standard draft 6 can be signaled as in the following table.

Additionally, for example, in VVC standard draft 5, chroma QP control is only available at the picture and slice level. For example, chroma QP can be derived as follows:

Here, Qp _Y is luma QP, QpBdOffset _C is chroma QP range offset, pps_cb_qp_offset, pps_cr_qp_offset, pps_joint_cbcr_qp_offset is PPS level QP offset for each chroma component, slice_cb_qp_offset, slice_cr_qp_offset, slice_joint_cbcr_qp _offset is the slice for each chroma component May indicate level QP offset. Additionally, Qp' _Cb may represent a chroma quantization parameter for the chroma Cb component, Qp' _Cr may represent a chroma quantization parameter for the chroma Cr component, and Qp' _CbCr may represent a chroma quantization parameter for joint Cb-Cr coding.

Additionally, for example, in VVC standard draft 6, CU level chroma QP control is also applied. For example, chroma QP can be derived as follows:

Here, CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr may represent the CU level QP offset for each chroma component. Additionally, Qp' _Cb may represent a chroma quantization parameter for the chroma Cb component, Qp' _Cr may represent a chroma quantization parameter for the chroma Cr component, and Qp' _CbCr may represent a chroma quantization parameter for joint Cb-Cr coding.

Figure 8 shows an example of a QP map for a luma block and a chroma block when a single tree is used. CU chroma QPs can be derived as the sum of luma QP and signaled chroma QP offset. Referring to FIG. 8, a square indicated by a solid line may represent a quantization group, and a square indicated by a dotted line may represent a CU. Also, for example, referring to FIG. 8, CuQpOffset _chroma may be 2. Meanwhile, the tree type of the current block can be classified into a single tree (SINGLE_TREE) or a dual tree (DUAL_TREE) depending on whether the current luma block and the corresponding current chroma blocks have individual partition structures. For example, if the current chroma blocks have the same partition structure as the current luma block, they can be represented as a single tree, and if the current chroma blocks have a different partition structure than the current luma block, they can be represented as a dual tree. The current block may be CU or TU.

Figure 9 shows an example of a QP map for a chroma block when a dual tree is used. Additionally, for example, referring to (a) of FIG. 9, CuQpOffset _chroma may be -9, and referring to (b) of FIG. 9, CuQpOffset _chroma may be 2. When a dual tree is used, the luma CU and chroma CU boundaries may not be aligned. That is, chroma blocks may have a different division structure than the corresponding luma block. Therefore, for each chroma CU, the chroma QP can be derived as the sum of the co-located luma QP (at the center of the chroma CU) and the signaled chroma QP offset. Although some correlation between luma QP and chroma QP is maintained, control over chroma QP can be difficult to predict.

Additionally, VVC Standard Draft 6 incorporates the joint CbCr residual coding mode by extending the offset table from 2 QPoffsets per entry to 3 QPoffsets per entry.

Additionally, for example, the TU syntax of VVC Standard Draft 6 may be as shown in the table below.

The transform coefficient level can be expressed as an array TransCoeffLevel[x0][y0][cIdx][xC][yC]. Here, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block with respect to the top left luma sample of the picture. That is, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block when the position of the top left luma sample of the picture is (0, 0). Additionally, the array index cIdx may represent an index for a color component. For example, the array index value for the luma component (Y component) may be equal to 0, the array index value for the chroma Cb component may be equal to 1, and the array index value for the chroma Cr component may be equal to 2. Additionally, array indices xC and yC may indicate the positions (xC, yC) of transform coefficients within the current transform block. Meanwhile, if the value of TransCoeffLevel[x0][y0][cIdx][xC][yC] is not specified, the value may be considered (inferred) to be equal to 0.

Additionally, for example, if the syntax element tu_cbf_cb[x0][y0] is 1, it may indicate that the Cb transform block includes one or more transform coefficient levels other than 0. Here, the array index x0, y0 may indicate the upper left position (x0, y0) of the transform block being considered. If the syntax element tu_cbf_cb[x0][y0] does not exist in the current TU, the value of the syntax element tu_cbf_cb[x0][y0] may be considered 0. Additionally, the tu_cbf_cb[x0][y0] may be expressed as tu_cb_coded_flag[x0][y0].

Additionally, for example, if the syntax element tu_cbf_cr[x0][y0] is 1, it may indicate that the Cr transform block includes one or more transform coefficient levels other than 0. Here, the array index x0, y0 may indicate the upper left position (x0, y0) of the transform block being considered. If the syntax element tu_cbf_cr[x0][y0] does not exist in the current TU, the value of the syntax element tu_cbf_cr[x0][y0] may be considered 0. Additionally, the tu_cbf_cr[x0][y0] may be expressed as tu_cr_coded_flag[x0][y0].

Additionally, for example, if the syntax element tu_cbf_luma[x0][y0] is 1, it may indicate that the luma transform block includes one or more transform coefficient levels other than 0. Here, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block with respect to the top left luma sample of the picture. That is, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block when the position of the top left luma sample of the picture is (0, 0). If the syntax element tu_cbf_luma[x0][y0] does not exist in the current TU, the value of the syntax element tu_cbf_luma[x0][y0] can be considered as follows.

For example, if the value of cu_sbt_flag is 1 and one of the conditions described later is true, the value of the syntax element tu_cbf_luma[x0][y0] may be regarded as 0.

- When the value of subTuIndex is 0 and the value of cu_sbt_pos_flag is 1

- When the value of subTuIndex is 1 and the value of cu_sbt_pos_flag is 0

Meanwhile, in other cases, the value of the syntax element tu_cbf_luma[x0][y0] can be regarded as 1. Additionally, the tu_cbf_luma[x0][y0] may be expressed as tu_y_coded_flag[x0][y0].

Additionally, for example, the syntax element tu_joint_cbcr_residual_flag[x0][y0] may indicate whether residual samples for the chroma component Cb and the chroma component Cr are coded with a single transform block. Here, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block with respect to the top left luma sample of the picture. That is, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block when the position of the top left luma sample of the picture is (0, 0).

For example, if the syntax element tu_joint_cbcr_residual_flag[x0][y0] is 1, the transform unit syntax contains the transform coefficient level for a single transform block from which the residual samples for the chroma component Cb and the chroma component Cr are derived. It can indicate that Also, for example, if the syntax element tu_joint_cbcr_residual_flag[x0][y0] is 0, then the transform coefficient levels of the chroma components are coded as indicated by the syntax elements tu_cbf_cb[x0][y0] and tu_cbf_cr[x0][y0]. It can be expressed. If the syntax element tu_joint_cbcr_residual_flag[x0][y0] does not exist, the value of the syntax element tu_joint_cbcr_residual_flag[x0][y0] may be considered 0.

For example, the variable TuCResMode[x0][y0] can be derived according to tu_joint_cbcr_residual_flag[x0][y0], tu_cbf_cb[x0][y0], and tu_cbf_cr[x0][y0] as follows.

- For example, if the value of tu_joint_cbcr_residual_flag[x0][y0] is 0, the variable TuCResMode[x0][y0] can be set to 0.

- If the above-mentioned case does not apply and tu_cbf_cb[x0][y0] is 1 and tu_cbf_cr[x0][y0] is 0, the variable TuCResMode[x0][y0] can be set to 1.

- If the above-mentioned case does not apply and tu_cbf_cb[x0][y0] is 1, the variable TuCResMode[x0][y0] can be set to 2.

- If the above-mentioned case does not apply, the variable TuCResMode[x0][y0] can be set to 3.

Additionally, for example, the syntax element cu_qp_delta_abs may indicate the absolute value of the difference CuQpDeltaVal between the quantization parameter of the current coding unit and its prediction.

Additionally, for example, the syntax element cu_qp_delta_sign_flag can indicate the sign of CuQpDeltaVal as follows.

- For example, if cu_qp_delta_sign_flag is 0, the corresponding CuQpDeltaVal may have a positive value.

- If the above-mentioned case does not apply (i.e., for example, when cu_qp_delta_sign_flag is 1), the corresponding CuQpDeltaVal may have a negative value.

Meanwhile, if the syntax element cu_qp_delta_sign_flag does not exist, the value of the syntax element cu_qp_delta_sign_flag may be regarded as 0.

Also, for example, if cu_qp_delta_abs exists, the variable IsCuQpDeltaCoded and the variable CuQpDeltaVal can be derived as in the following equation.

The value of CuQpDeltaVal may be in the range of -(32 + QpBdOffsetY / 2) to +(31 + QpBdOffsetY / 2).

Also, for example, if the syntax element cu_chroma_qp_offset_flag exists and is 1, the syntax element cu_chroma_qp_offset_flag is an entry in cb_qp_offset_list[] is used to determine the value of CuQpOffset _Cb , and the corresponding entry in cr_qp_offset_list[] is used to determine the value of CuQpOffset _Cr . It is used to determine the value, and may indicate that the corresponding entry in joint_cbcr_qp_offset_list[] is used to determine the value of CuQpOffset _CbCr . Additionally, for example, when the syntax element cu_chroma_qp_offset_flag is 0, the syntax element cu_chroma_qp_offset_flag is cb_qp_offset_list[], cr_qp_offset_list[], joint_cbcr_qp_offset_list[] of CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr. Can indicate that it is not used to determine values. there is.

Also, for example, if the syntax element cu_chroma_qp_offset_idx is present, the syntax element cu_chroma_qp_offset_idx is used to determine the values of CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr , cb_qp_offset_list[], cr_qp_offset_list[], and joint_cbcr_qp_offset_list. [] can indicate the index in there is. If the syntax element cu_chroma_qp_offset_idx exists, the value of the syntax element cu_chroma_qp_offset_idx may be in the range of 0 to chroma_qp_offset_list_len_minus1. If the syntax element cu_chroma_qp_offset_idx does not exist, the syntax element cu_chroma_qp_offset_idx may be considered 0.

Additionally, for example, if the syntax element cu_chroma_qp_offset_flag exists, the content described later may be applied.

- If cu_chroma_qp_offset_flag is 1, the values of CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr can be derived as in the following equation.

- If the above-mentioned case does not apply (i.e., for example, when cu_chroma_qp_offset_flag is 0), CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr may be set to 0.

Additionally, for example, the syntax element transform_skip_flag[x0][y0] may indicate whether a transform is applied to the luma transform block. Here, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block with respect to the top left luma sample of the picture. That is, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block when the position of the top left luma sample of the picture is (0, 0). For example, if transform_skip_flag[x0][y0] is 1, it may indicate that transform is not applied to the luma transform block. Additionally, for example, if transform_skip_flag[x0][y0] is 0, it may indicate that whether a transform is applied to the luma transform block may be determined based on other syntax elements.

Additionally, for example, if the transform_skip_flag[x0][y0] does not exist, the value of transform_skip_flag[x0][y0] may be considered as follows.

- For example, if BdpcmFlag[x0][y0] is 1, transform_skip_flag[x0][y0] can be considered 1.

- If the above-mentioned case does not apply (i.e., for example, when BdpcmFlag[x0][y0] is 0), the transform_skip_flag[x0][y0] may be regarded as 0.

Additionally, for example, the syntax element tu_mts_idx[x0][y0] may represent transform kernels applied to residual samples in the horizontal and vertical directions of the associated luma transform block. Here, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block with respect to the top left luma sample of the picture. That is, the array index x0, y0 may indicate the position (x0, y0) of the top left luma sample of the corresponding transform block when the position of the top left luma sample of the picture is (0, 0). Additionally, for example, if the syntax element tu_mts_idx[x0][y0] does not exist, the syntax element tu_mts_idx[x0][y0] may be regarded as 0.

Figure 10 exemplarily shows sample positions for deblocking filtering.

Meanwhile, chroma QP can be used for deblocking filtering of chroma components. However, for example, chroma QP used for deblocking filtering may not consider slice level and CU level QP adjustment. For example, the chroma QP used for deblocking filtering can be derived based on the corresponding luma QP and picture level chroma QP offset cQpPicOffset. Here, for example, cQpPicOffset, which represents the picture level chroma QP offset, can be derived as pps_cb_qp_offset if cIdx is 1, and if cIdx is not 1, it can be derived as pps_cr_qp_offset.

Additionally, for example, the variable Qp _Q may be set equal to the Qp _Y value of the coding unit including the coding block containing sample q _0,0 shown in FIG. 6, and the variable Qp _P may be set equal to the Qp Y value shown in FIG. 6 It may be set equal to the Qp _Y value of the coding unit including the coding block including the sample p _0,0 .

Afterwards, the chroma QP Qp _C used for deblocking filtering can be derived as in the following equation.

Meanwhile, the Chroma QP-related design for deblocking filtering in the existing VVC standard may have some drawbacks. Since VVC supports dual trees, there may be a big difference between the CU's luma QP and chroma QP because the partitions of the luma block and chroma block are different. Additionally, the VVC standard supports not only the YUV 4:2:0 format, but also the YUV 4:2:2 format and YUV 4:4:4 format. Here, in the case of the YUV 4:4:4 format, if an inaccurate chroma QP is used for deblocking filtering, it may have a greater impact and visual artefacts may occur.

Accordingly, this document proposes an efficient chroma QP signaling method, such as the embodiments described later.

In one embodiment, we propose chroma QP offset signaling that supports VDPU level processing. In this embodiment, for a chroma CU with cbWidth or cbHeight greater than 64, the CU chroma QP offset (a chroma QP offset for the chroma CU exists) regardless of whether the first TU contains a non-zero chroma CBF. case) may be signaled. That is, according to this embodiment, if the cbWidth or cbHeight of the current chroma CU is greater than 64, the CU chroma QP offset (chroma QP for the chroma CU) regardless of whether the first TU has a non-zero coefficient. If an offset exists) may be signaled. Here, the cbWidth and cbHeight may represent the CU width and CU height of the luma element or chroma element according to the channel type or tree type. For example, in the case of an image in YUV 4:4:4 format, a chroma CU with a width or height greater than 64 may occur, and the method proposed in this embodiment enables VDPU level processing and allows the VDPU to be parsed. When QP may be available.

For example, the conversion unit syntax according to this embodiment may be as shown in the following table.

Referring to Table 3, the signaling condition for CU chroma QP offset-related information includes "CbWidth[chType][x0][y0] > 64 || CbHeight[chType][x0][y0] > 64 ||" can be added. That is, referring to Table 3, when CbWidth[chType][x0][y0] is greater than 64 or when CbHeight[chType][x0][y0] is greater than 64, CU chroma QP offset-related information may be signaled. . The CU chroma QP offset-related information may include the syntax element cu_chroma_qp_offset_flag and/or the syntax element cu_chroma_qp_offset_idx.

For example, if the syntax element cu_chroma_qp_offset_flag exists and is 1, the syntax element cu_chroma_qp_offset_flag is an entry in cb_qp_offset_list[] used to determine the value of CuQpOffset _Cb , and the corresponding entry in cr_qp_offset_list[] determines the value of CuQpOffset _Cr . It is used to determine, and may indicate that the corresponding entry in joint_cbcr_qp_offset_list[] is used to determine the value of CuQpOffset _CbCr . Additionally, for example, when the syntax element cu_chroma_qp_offset_flag is 0, the syntax element cu_chroma_qp_offset_flag is cb_qp_offset_list[], cr_qp_offset_list[], joint_cbcr_qp_offset_list[] of CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr. Can indicate that it is not used to determine values. there is.

Also, for example, if the syntax element cu_chroma_qp_offset_idx is present, the syntax element cu_chroma_qp_offset_idx is used to determine the values of CuQpOffset _Cb , CuQpOffset _Cr , and CuQpOffset _CbCr , cb_qp_offset_list[], cr_qp_offset_list[], and joint_cbcr_qp_offset_list. [] can indicate the index in there is. If the syntax element cu_chroma_qp_offset_idx exists, the value of the syntax element cu_chroma_qp_offset_idx may be in the range of 0 to chroma_qp_offset_list_len_minus1. If the syntax element cu_chroma_qp_offset_idx does not exist, the syntax element cu_chroma_qp_offset_idx may be considered 0.

Additionally, as an embodiment, this document proposes a method of adding conditions to CU level chroma QP offset signaling for dual trees. This embodiment proposes a method of modifying the availability conditions of the existing syntax for the CU chroma QP offset flag to avoid unnecessary signaling. For example, according to this embodiment, if the coding tree is a dual tree chroma (DUAL_TREE_LUMA), that is, if the coding tree is not a single tree (SINGLE_TREE) and a dual tree chroma (DUAL_TREE_CHROMA), CU chroma QP Offset-related information may not be signaled.

For example, the conversion unit syntax according to this embodiment may be as shown in the following table.

Referring to Table 4, "&& treeType != DUAL_TREE_LUMA" can be added to the signaling condition for CU chroma QP offset-related information. That is, referring to Table 4, CU chroma QP offset-related information can be signaled only when the coding tree is not DUAL_TREE_LUMA. The CU chroma QP offset-related information may include the syntax element cu_chroma_qp_offset_flag and/or the syntax element cu_chroma_qp_offset_idx.

Additionally, as an embodiment, this document proposes another method of adding conditions to CU level chroma QP offset signaling. This embodiment proposes a method of modifying the availability conditions of the existing syntax for the CU chroma QP offset flag to avoid unnecessary signaling. For example, this embodiment proposes a method of modifying the availability conditions of existing syntax by combining the signaling conditions of the above-described embodiments.

For example, the conversion unit syntax according to this embodiment may be as shown in the following table.

Referring to Table 5, the signaling condition for CU chroma QP offset-related information includes "CbWidth[chType][x0][y0] > 64 || CbHeight[chType][x0][y0] > 64 ||" and "&& treeType != DUAL_TREE_LUMA" can be added. That is, referring to Table 5, if the coding tree is not DUAL_TREE_LUMA and CbWidth[chType][x0][y0] is greater than 64, or CbHeight[chType][x0][y0] is greater than 64, the CU chroma QP offset Relevant information may be signaled. Therefore, if the coding tree is DUAL_TREE_LUMA, CU chroma QP offset-related information may not be signaled. The CU chroma QP offset-related information may include the syntax element cu_chroma_qp_offset_flag and/or the syntax element cu_chroma_qp_offset_idx.

Additionally, this document proposes a method of using CU level chroma QP for deblocking filtering. This embodiment proposes a method of integrating slice-level chroma QP and/or CU-level chroma QP into chroma QP, denoted as QpC, used in the chroma deblocking process. Deblocking parameters can be determined based on the derived QpC.

For example, the variable QpC can be derived based on the Qp of surrounding CUs as shown in the following equation.

Here, Qp _Q'cIdx may represent the chroma QP of CU P adjacent to the block boundary to be deblocked filtered, and Qp _P'cIdx may represent the chroma QP of CU Q adjacent to the block boundary to be deblocked filtered. Additionally, cIdx may be an index representing a chroma component. For example, cIdx may represent a chroma Cb component, a chroma Cr component, or a chroma CbCr component. Qp _Q'cIdx and Qp _P'cIdx may be values for which slice level QP adjustment and CU level QP adjustment have already been considered.

Or, for example, the variable QpC may first be derived based on the luma QP of the surrounding CU P and the surrounding CU Q, and then slice level QP adjustment and CU level QP adjustment may be added. For example, the variable QpC can be derived as the following equation.

Here, CuQpOffset _PcIdx may represent CuQPOffset of element cIdx of the surrounding CU P, and CuQpOffset _QcIdx may represent CuQPOffset of element cIdx of the surrounding CU Q.

Figure 11 schematically shows an image encoding method using an encoding device according to this document. The method disclosed in FIG. 11 may be performed by the encoding device disclosed in FIG. 2. Specifically, for example, S1100 to S1140 of FIG. 11 may be performed by the residual processing unit of the encoding device, and S1150 may be performed by the entropy encoding unit of the encoding device. In addition, although not shown, the process of deriving prediction samples of the current chroma block may be performed by a prediction unit of the encoding device, and may produce restored samples and restored pictures based on the residual samples and the predicted samples. The generating process may be performed by the addition unit of the encoding device.

The encoding device derives residual samples for the current chroma block (S1100). The encoding device can derive residual samples for the current chroma block.

For example, the encoding device may derive prediction samples of the current chroma block based on the prediction mode. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, can be applied.

For example, the encoding device can determine whether to perform inter-prediction or intra-prediction on the current chroma block, and can determine a specific inter-prediction mode or a specific intra-prediction mode based on the RD cost. According to the determined mode, the encoding device can derive prediction samples for the current chroma block. Thereafter, for example, the encoding device may derive the residual samples by subtracting the original samples for the current chroma block and the prediction samples.

The encoding device generates information related to the coding unit (CU) chroma quantization parameter (QP) offset for the current chroma block based on the size and tree type of the current chroma block (S1110). .

The encoding device may generate information related to the CU chroma quantization parameter (QP) offset for the current chroma block based on the size and tree type of the current chroma block. The CU chroma QP offset-related information may also be expressed as CU-level chroma QP offset-related information. Here, the tree type may be one of single tree, dual tree luma, and dual tree chroma. Additionally, for example, the CU chroma QP offset-related information may be signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block. That is, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset. The first transform block may be a transform block coded first in decoding order among transform blocks of the current chroma block. For example, the first transform block may be the upper left transform block among the transform blocks of the current chroma block.

Specifically, for example, when at least one of the width and height of the current chroma block is greater than a specific value, the CU chroma QP offset-related information for the current chroma block may be signaled. That is, for example, when at least one of the width and height of the current chroma block is greater than a specific value, the CU chroma QP offset related information for the current chroma block may be generated. Here, for example, the specific value may be 64. Additionally, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, if at least one of the width and height of the current chroma block is greater than a specific value, regardless of whether the first transform block includes at least one non-zero transform coefficient level, the first transform block The CU chroma QP offset-related information for the current chroma block may be signaled in the transform unit syntax for the transform block. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value, the relationship is whether the first transform block includes at least one non-zero transform coefficient level. The transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block.

Or, for example, when the tree type is the dual tree luma, the CU chroma QP offset related information for the current chroma block may not be signaled. That is, for example, when the tree type is the dual tree luma, the CU chroma QP offset related information for the current chroma block may not be generated. Therefore, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the CU chroma QP offset related information for the current chroma block is It can be signaled. That is, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the CU chroma QP offset related information for the current chroma block is can be created. Here, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the first transform block includes at least one non-zero transform coefficient level. Regardless of whether or not, the CU chroma QP offset-related information for the current chroma block may be signaled through the transform unit syntax for the first transform block. That is, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the first transform block has at least one non-zero transform coefficient level. Regardless of whether it includes the transform unit syntax for the first transform block, it may include information related to the CU chroma QP offset for the current chroma block.

Or, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is single tree and luma) (in the case of one of dual tree chroma), the CU chroma QP offset related information for the current chroma block may be signaled. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is one of single tree and dual tree chroma) case), the CU chroma QP offset-related information for the current chroma block may be generated. Here, for example, the specific value may be 64. Therefore, for example, when the tree type is the dual tree luma, the CU chroma QP offset related information for the current chroma block may not be signaled. Additionally, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, when at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., when the tree type is one of single tree and dual tree chroma) , the CU chroma QP offset related information for the current chroma block can be signaled through the transform unit syntax for the first transform block regardless of whether the first transform block includes at least one non-zero transform coefficient level. there is. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is one of single tree and dual tree chroma) case), regardless of whether the first transform block includes at least one non-zero transform coefficient level, the transform unit syntax for the first transform block will include information related to the CU chroma QP offset for the current chroma block. You can.

Meanwhile, for example, the CU chroma QP offset-related information may include a CU chroma QP offset flag and/or a CU chroma QP offset index for the current chroma block. The CU chroma QP offset flag may be expressed as a CU level chroma QP offset flag, and the CU chroma QP offset index may be expressed as a CU level chroma QP offset index.

For example, the CU chroma QP offset flag may be a flag indicating whether an entry in the CU QP offset list for the chroma component is used to determine the value of the CU chroma QP offset. That is, for example, the CU chroma QP offset flag may indicate whether an entry in the CU QP offset list for the chroma component is used to determine the value of the CU chroma QP offset. For example, if the CU chroma QP offset flag exists and the value of the CU chroma QP offset flag is 1, the CU chroma QP offset flag indicates that the entry in the CU QP offset list for the chroma component is CU chroma. It may indicate that it is used to determine the value of the QP offset. Additionally, for example, when the value of the CU chroma QP offset flag is 0, the CU chroma QP offset flag may indicate that the CU QP offset list for the chroma component is not used to determine the value of the CU chroma QP offset. there is. Here, for example, the chroma component may include a Cb component, a Cr component, and/or a joint CbCr component. Additionally, for example, the syntax element of the CU chroma QP offset flag may be the cu_chroma_qp_offset_flag described above.

Additionally, for example, the CU chroma QP offset index may indicate the index of an entry in the CU QP offset list used to determine the value of the CU chroma QP offset. That is, for example, the CU chroma QP offset index may be information about the index of an entry in the CU QP offset list. Additionally, for example, the syntax element of the CU chroma QP offset index may be cu_chroma_qp_offset_idx described above.

The encoding device derives the chroma QP for the current chroma block based on the CU chroma QP offset-related information (S1120). The encoding device may derive the chroma QP for the current chroma block based on the CU chroma QP offset-related information. For example, the encoding device may derive the CU chroma QP offset for the current chroma block based on the CU chroma QP offset-related information, and may derive the chroma QP for the current chroma block based on the CU chroma QP offset. It can be derived. Specifically, for example, the encoding device may derive the chroma QP for the current chroma block through addition of the first chroma QP for the chroma component and the CU chroma QP offset.

Specifically, for example, the encoding device may derive a first chroma QP for the chroma component of the current chroma block based on a luma QP and/or chroma QP mapping table, and the CU chroma QP offset related A CU chroma QP offset for the current chroma block can be derived based on the information, and a chroma QP for the current chroma block can be derived based on the first chroma QP and the CU chroma QP offset. Here, for example, the first chroma QP may be referred to as a SPS (Sequence Parameter Set) chroma QP or an SPS level chroma QP.

The encoding device quantizes the residual samples based on the chroma QP and derives transform coefficients for the current chroma block (S1130). The encoding device may derive transform coefficients for the current chroma block based on the chroma QP. For example, the encoding device may quantize the residual samples for the current chroma block based on the chroma QP to derive the transform coefficients. Or, for example, the decoding device may derive transformed transform coefficients by transforming the residual samples for the current chroma block, and quantize the transformed transform coefficients based on the chroma QP to generate the transform coefficients. It can be derived.

The encoding device generates residual information about the transform coefficients (S1140). For example, the encoding device may generate and encode residual information about the transform coefficients. For example, the residual information may include transform coefficient level information and sine flag information for the transform coefficients. For example, the transform coefficient level of the transform coefficient may be derived from the value indicated by the transform coefficient level information included in the residual information, and the sign of the transform coefficient may be derived from the sign indicated by the sign flag information. there is. For example, the residual information may include syntax elements for transform coefficients of the current chroma block. For example, the syntax elements may include coded_sub_block_flag, sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag, abs_remainder, and/or coeff_sign_flag.

The encoding device encodes image information including the CU chroma QP offset-related information and the residual information (S1150). The encoding device may encode the CU chroma QP offset-related information and the residual information. Image information may include the CU chroma QP offset-related information and the residual information.

Meanwhile, for example, an encoding device may generate and encode prediction information for the current chroma block. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, can be applied. For example, the encoding device can determine whether to perform inter-prediction or intra-prediction on the current chroma block, and can determine a specific inter-prediction mode or a specific intra-prediction mode based on the RD cost. According to the determined mode, the encoding device can derive prediction samples for the current chroma block. The prediction information may include prediction mode information for the current chroma block. The image information may include the prediction information.

Additionally, for example, an encoding device may encode video information and output it in the form of a bitstream.

Meanwhile, for example, an encoding device may generate reconstructed samples and/or a reconstructed picture by adding the prediction samples and the residual samples.

As described above, in-loop filtering procedures such as deblocking filtering, SAO and/or ALF procedures can be applied to the restored samples to improve subjective/objective image quality as needed.

Meanwhile, for example, deblocking filtering may be performed on the edge of the current chroma block. For example, a specific value may be derived based on the chroma QP of the current chroma block and the chroma QP of a neighboring block of the current chroma block adjacent to the edge, and deblocking for the deblocking filtering is performed based on the specific value. A deblocking parameter may be derived. For example, the specific value can be derived as in Equation 6 described above. As described above, the chroma QP of the current chroma block may be derived based on the CU chroma QP offset for the current chroma block, and the chroma QP of the neighboring block may be derived based on the CU chroma QP offset for the neighboring block. can be derived. Here, for example, the edge may indicate an area of the current chroma block to which the deblocking filtering is applied.

Or, for example, a specific value may be derived based on the chroma QP of the current chroma block, the chroma QP of a neighboring block of the current chroma block adjacent to the edge, and the CU chroma QP offset, and based on the specific value A deblocking parameter for the deblocking filtering can be derived. For example, the specific value can be derived as in Equation 7 described above. Here, for example, the edge may indicate an area of the current chroma block to which the deblocking filtering is applied.

Meanwhile, a bitstream containing the video information may be transmitted to a decoding device through a network or (digital) storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

Figure 12 schematically shows an encoding device that performs the image encoding method according to this document. The method disclosed in FIG. 11 may be performed by the encoding device disclosed in FIG. 12. Specifically, for example, the residual processing unit of the encoding device of FIG. 12 may perform S1100 to S1140, and the entropy encoding unit of the encoding device of FIG. 12 may perform S1150. In addition, although not shown, the process of deriving prediction samples of the current chroma block may be performed by a prediction unit of the encoding device, and may produce restored samples and restored pictures based on the residual samples and the predicted samples. The generating process may be performed by the addition unit of the encoding device.

Figure 13 schematically shows a video decoding method using a decoding device according to this document. The method disclosed in FIG. 13 may be performed by the decoding device disclosed in FIG. 3. Specifically, for example, S1300 to S1310 of FIG. 13 may be performed by the entropy decoding unit of the decoding device, and S1320 to S1340 of FIG. 13 may be performed by the residual processing unit of the decoding device, and FIG. 13 S1350 may be performed by the addition unit of the decoding device.

The decoding device obtains residual information about the current chroma block (S1300). A decoding device can acquire video information through a bitstream. For example, the image information may include residual information about the current chroma block. For example, the residual information may include syntax elements for transform coefficients of the current chroma block. For example, the syntax elements may include coded_sub_block_flag, sig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag, abs_remainder, and/or coeff_sign_flag.

The decoding device obtains information related to the coding unit (CU) chroma quantization parameter (QP) offset for the current chroma block based on the size and tree type of the current chroma block (S1310 ).

The decoding device may obtain information related to the CU chroma quantization parameter (QP) offset for the current chroma block based on the size and tree type of the current chroma block. For example, the image information may include information related to the CU chroma QP offset. The CU chroma QP offset-related information may also be expressed as CU-level chroma QP offset-related information. Here, the tree type may be one of single tree, dual tree luma, and dual tree chroma. Additionally, for example, the CU chroma QP offset-related information may be signaled as transform unit syntax for the first transform block among transform blocks of the current chroma block. That is, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset. The first transform block may be a transform block that is decoded first in decoding order among transform blocks of the current chroma block. For example, the first transform block may be the upper left transform block among the transform blocks of the current chroma block.

Specifically, for example, when at least one of the width and height of the current chroma block is greater than a specific value, the CU chroma QP offset-related information for the current chroma block may be signaled. That is, for example, when at least one of the width and height of the current chroma block is greater than a specific value, the CU chroma QP offset-related information for the current chroma block can be obtained. Here, for example, the specific value may be 64. Additionally, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, if at least one of the width and height of the current chroma block is greater than a specific value, regardless of whether the first transform block includes at least one non-zero transform coefficient level, the first transform block Information related to the CU chroma QP offset for the current chroma block can be obtained with transform unit syntax for the transform block. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value, the relationship is whether the first transform block includes at least one non-zero transform coefficient level. The transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block.

Or, for example, when the tree type is the dual tree luma, the CU chroma QP offset related information for the current chroma block may not be signaled. That is, for example, when the tree type is the dual tree luma, the CU chroma QP offset-related information for the current chroma block may not be obtained. Therefore, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the CU chroma QP offset related information for the current chroma block is It can be signaled. That is, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the CU chroma QP offset related information for the current chroma block is can be obtained. Here, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the first transform block includes at least one non-zero transform coefficient level. Regardless of whether the CU chroma QP offset for the current chroma block is obtained through the transform unit syntax for the first transform block. That is, for example, if the tree type is not the dual tree luma (i.e., if the tree type is one of single tree and dual tree chroma), the first transform block has at least one non-zero transform coefficient level. Regardless of whether it includes the transform unit syntax for the first transform block, it may include information related to the CU chroma QP offset for the current chroma block.

Or, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is single tree and luma) (in the case of one of dual tree chroma), the CU chroma QP offset related information for the current chroma block may be signaled. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is one of single tree and dual tree chroma) case), the CU chroma QP offset-related information for the current chroma block can be obtained. Here, for example, the specific value may be 64. Therefore, for example, when the tree type is the dual tree luma, the CU chroma QP offset related information for the current chroma block may not be signaled. Additionally, for example, the transform unit syntax for the first transform block may include information related to the CU chroma QP offset for the current chroma block. For example, when at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., when the tree type is one of single tree and dual tree chroma) , The CU chroma QP offset-related information for the current chroma block can be obtained through the transform unit syntax for the first transform block regardless of whether the first transform block includes at least one non-zero transform coefficient level. there is. That is, for example, if at least one of the width and height of the current chroma block is greater than a specific value and the tree type is not the dual tree luma (i.e., the tree type is one of single tree and dual tree chroma) case), regardless of whether the first transform block includes at least one non-zero transform coefficient level, the transform unit syntax for the first transform block will include information related to the CU chroma QP offset for the current chroma block. You can.

Meanwhile, for example, the CU chroma QP offset-related information may include a CU chroma QP offset flag and/or a CU chroma QP offset index for the current chroma block. The CU chroma QP offset flag may be expressed as a CU level chroma QP offset flag, and the CU chroma QP offset index may be expressed as a CU level chroma QP offset index.

For example, the CU chroma QP offset flag may be a flag indicating whether an entry in the CU QP offset list for the chroma component is used to determine the value of the CU chroma QP offset. That is, for example, the CU chroma QP offset flag may indicate whether an entry in the CU QP offset list for the chroma component is used to determine the value of the CU chroma QP offset. For example, if the CU chroma QP offset flag exists and the value of the CU chroma QP offset flag is 1, the CU chroma QP offset flag indicates that the entry in the CU QP offset list for the chroma component is CU chroma. It may indicate that it is used to determine the value of the QP offset. Additionally, for example, when the value of the CU chroma QP offset flag is 0, the CU chroma QP offset flag may indicate that the CU QP offset list for the chroma component is not used to determine the value of the CU chroma QP offset. there is. Here, for example, the chroma component may include a Cb component, a Cr component, and/or a joint CbCr component. Additionally, for example, the syntax element of the CU chroma QP offset flag may be the cu_chroma_qp_offset_flag described above.

Additionally, for example, the CU chroma QP offset index may indicate the index of an entry in the CU QP offset list used to determine the value of the CU chroma QP offset. That is, for example, the CU chroma QP offset index may be information about the index of an entry in the CU QP offset list. Additionally, for example, the syntax element of the CU chroma QP offset index may be cu_chroma_qp_offset_idx described above.

The decoding device derives transform coefficients for the current chroma block based on the residual information (S1320). The decoding device may derive transform coefficients of the current chroma block based on the residual information. The residual information may include transform coefficient level information and sine flag information for the transform coefficients.

For example, the transform coefficient level of the transform coefficient may be derived from the value indicated by the transform coefficient level information included in the residual information, and the sign of the transform coefficient may be derived from the sign indicated by the sign flag information. there is.

The decoding device derives the chroma QP for the current chroma block based on the CU chroma QP offset-related information (S1330). The decoding device may derive the chroma QP for the current chroma block based on the CU chroma QP offset-related information. For example, the decoding device may derive the CU chroma QP offset for the current chroma block based on the CU chroma QP offset-related information, and may derive the chroma QP for the current chroma block based on the CU chroma QP offset. It can be derived. Specifically, for example, the decoding device may derive the chroma QP for the current chroma block through addition of the first chroma QP and the CU chroma QP offset for the chroma component.

Specifically, for example, the decoding device may derive a first chroma QP for the chroma component of the current chroma block based on a luma QP and/or chroma QP mapping table, and the CU chroma QP offset related A CU chroma QP offset for the current chroma block can be derived based on the information, and a chroma QP for the current chroma block can be derived based on the first chroma QP and the CU chroma QP offset. Here, for example, the first chroma QP may be referred to as a SPS (Sequence Parameter Set) chroma QP or an SPS level chroma QP.

The decoding device dequantizes the transform coefficients based on the chroma QP to derive residual samples for the current chroma block (S1340). The decoding device may derive residual samples for the current chroma block based on the chroma QP. For example, the decoding device may dequantize the transform coefficients for the current chroma block based on the chroma QP to derive the residual samples. Or, for example, the decoding device may inversely transform the transform coefficients for the current chroma block to derive inverse transform coefficients, and inversely quantize the inverse transform coefficients based on the chroma QP to generate the residual sample. can be derived.

The decoding device generates a restored picture based on the residual samples (S1350). For example, a decoding device may generate the reconstructed picture based on the residual samples.

Meanwhile, for example, the decoding device may perform an inter prediction mode or an intra prediction mode for the current chroma block based on prediction information received through a bitstream to derive prediction samples, and the prediction samples and the Reconstructed samples and/or restored pictures can be generated through addition of residual samples.

As described above, in-loop filtering procedures such as deblocking filtering, SAO and/or ALF procedures can be applied to the restored samples to improve subjective/objective image quality as needed.

Meanwhile, for example, deblocking filtering may be performed on the edge of the current chroma block. For example, a specific value may be derived based on the chroma QP of the current chroma block and the chroma QP of a neighboring block of the current chroma block adjacent to the edge, and deblocking for the deblocking filtering is performed based on the specific value. A deblocking parameter may be derived. For example, the specific value can be derived as in Equation 6 described above. As described above, the chroma QP of the current chroma block may be derived based on the CU chroma QP offset for the current chroma block, and the chroma QP of the neighboring block may be derived based on the CU chroma QP offset for the neighboring block. can be derived. Here, for example, the edge may indicate an area of the current chroma block to which the deblocking filtering is applied.

Or, for example, a specific value may be derived based on the chroma QP of the current chroma block, the chroma QP of a neighboring block of the current chroma block adjacent to the edge, and the CU chroma QP offset, and based on the specific value A deblocking parameter for the deblocking filtering can be derived. For example, the specific value can be derived as in Equation 7 described above. Here, for example, the edge may indicate an area of the current chroma block to which the deblocking filtering is applied.

Figure 14 schematically shows a decoding device that performs the image decoding method according to this document. The method disclosed in FIG. 13 may be performed by the decoding device disclosed in FIG. 14. Specifically, for example, the entropy decoding unit of the decoding device of FIG. 14 may perform steps S1300 to S1310 of FIG. 13, and the residual processing unit of the decoding device of FIG. 14 may perform steps S1320 to S1340 of FIG. 13, , the adder of the decoding device of FIG. 14 may perform S1350 of FIG. 13.

According to this document described above, even if the first transform block in the current chroma block does not contain a transform coefficient level other than 0, if at least one of the width and height of the current chroma block is greater than a certain size, information about the CU chroma QP offset can be signaled. And through this, the cost for configuring the decoding device can be reduced.

In addition, according to this document, even if the first transform block in the current chroma block does not contain a non-zero transform coefficient level, the CU chroma QP offset is generated by the transform unit syntax of the first transform block based on the size and tree type of the current chroma block. Information can be signaled, which can reduce the buffer requirements of the decoding device and reduce the cost of constructing the decoding device.

In the above-described embodiments, the methods are described on the basis of flowcharts as a series of steps or blocks, but this document is not limited to the order of steps, and some steps may occur in a different order or simultaneously with other steps as described above. there is. Additionally, those skilled in the art will understand that the steps shown in the flowchart are not exclusive and that other steps may be included or one or more steps in the flowchart may be deleted without affecting the scope of the present document.

Embodiments described in this document may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units shown in each drawing may be implemented and performed on a computer, processor, microprocessor, controller, or chip. In this case, information for implementation (ex. information on instructions) or algorithm may be stored in a digital storage medium.

In addition, the decoding device and the encoding device to which the embodiments of this document are applied include real-time communication devices such as multimedia broadcasting transmission and reception devices, mobile communication terminals, home cinema video devices, digital cinema video devices, surveillance cameras, video conversation devices, and video communications. , mobile streaming devices, storage media, camcorders, video on demand (VoD) service provision devices, OTT video (Over the top video) devices, Internet streaming service provision devices, three-dimensional (3D) video devices, video phone video devices, and means of transportation. It may be included in terminals (ex. vehicle terminals, airplane terminals, ship terminals, etc.) and medical video devices, and may be used to process video signals or data signals. For example, OTT video (Over the top video) devices may include game consoles, Blu-ray players, Internet-connected TVs, home theater systems, smartphones, tablet PCs, and DVRs (Digital Video Recorders).

Additionally, the processing method to which the embodiments of this document are applied may be produced in the form of a program executed by a computer and stored in a computer-readable recording medium. Multimedia data having a data structure according to this document may also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices that store computer-readable data. The computer-readable recording media include, for example, Blu-ray Disk (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical media. May include a data storage device. Additionally, the computer-readable recording medium includes media implemented in the form of a carrier wave (eg, transmitted via the Internet). Additionally, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.

Additionally, the embodiments of this document can be implemented as a computer program product using program code, and the program code can be executed on a computer by the embodiments of this document. The program code may be stored on a carrier readable by a computer.

Figure 15 exemplarily shows a content streaming system structural diagram to which embodiments of this document are applied.

The content streaming system to which embodiments of this document are applied may largely include an encoding server, streaming server, web server, media storage, user device, and multimedia input device.

The encoding server compresses content input from multimedia input devices such as smartphones, cameras, camcorders, etc. into digital data, generates a bitstream, and transmits it to the streaming server. As another example, when multimedia input devices such as smartphones, cameras, camcorders, etc. directly generate bitstreams, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generation method to which embodiments of this document are applied, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

The streaming server transmits multimedia data to the user device based on user requests through a web server, and the web server serves as a medium to inform the user of what services are available. When a user requests a desired service from the web server, the web server delivers it to a streaming server, and the streaming server transmits multimedia data to the user. At this time, the content streaming system may include a separate control server, and in this case, the control server serves to control commands/responses between each device in the content streaming system.

The streaming server may receive content from a media repository and/or encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a certain period of time.

Examples of the user devices include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation, slate PCs, Tablet PC, ultrabook, wearable device (e.g. smartwatch, smart glass, head mounted display), digital TV, desktop There may be computers, digital signage, etc. Each server in the content streaming system may be operated as a distributed server, and in this case, data received from each server may be distributedly processed.

The claims set forth herein may be combined in various ways. For example, the technical features of the method claims of this specification may be combined to implement a device, and the technical features of the device claims of this specification may be combined to implement a method. Additionally, the technical features of the method claims of this specification and the technical features of the device claims may be combined to implement a device, and the technical features of the method claims of this specification and technical features of the device claims may be combined to implement a method.

Claims (16)

In an image decoding method performed by a decoding device,
Obtaining residual information about the chroma component of the current coding unit;
Obtaining information related to a Coding Unit (CU) chroma quantization parameter (QP) offset for the current coding unit based on the size and tree type of the current coding unit;
Deriving transform coefficients for the current coding unit based on the residual information;
Deriving a chroma QP for the current coding unit based on the CU chroma QP offset-related information;
Dequantizing the transform coefficients based on the chroma QP to derive residual samples for the current coding unit; and
Generating a restored picture based on the residual samples,
The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current coding unit,
A video decoding method, wherein the CU chroma QP offset-related information is obtained based on the fact that at least one of the width and height of the current coding unit is greater than 64 and the tree type is not dual tree luma. delete delete delete delete delete delete delete delete In a video encoding method performed by an encoding device,
Deriving residual samples for the chroma component of the current coding unit;
Deriving a chroma quantization parameter (QP) for the current coding unit;
quantizing the residual samples based on the chroma QP to derive transform coefficients for the current coding unit;
generating residual information about the transform coefficients;
generating coding unit (CU) chroma QP offset-related information for the chroma QP based on the size and tree type of the current coding unit; and
Comprising the step of encoding image information including the CU chroma QP offset related information and the residual information,
The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current coding unit,
A video encoding method, wherein the CU chroma QP offset-related information is signaled based on the fact that at least one of the width and height of the current coding unit is greater than 64 and the tree type is not dual tree luma. delete delete delete delete A computer-readable digital storage medium that stores a bitstream generated by a specific method, the specific method comprising:
Deriving residual samples for the chroma component of the current coding unit;
Deriving a chroma quantization parameter (QP) for the current coding unit;
quantizing the residual samples based on the chroma QP to derive transform coefficients for the current coding unit;
generating residual information about the transform coefficients;
generating coding unit (CU) chroma QP offset-related information for the chroma QP based on the size and tree type of the current coding unit;
Encoding image information including the CU chroma QP offset related information and the residual information; and
Generating the bitstream including the image information,
The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current coding unit,
A digital storage medium, wherein the CU chroma QP offset-related information is signaled based on the fact that at least one of the width and height of the current coding unit is greater than 64 and the tree type is not dual tree luma. In a method of transmitting data for video information,
A bit of image information including coding unit (CU) chroma quantization parameter (QP) offset-related information for the chroma component of the current coding unit and residual information about transform coefficients for the current coding unit. acquiring a stream; and
Transmitting the data including the bitstream of the image information including the CU chroma QP offset related information and the residual information,
The CU chroma QP offset-related information for the chroma QP for the current coding unit is generated based on the size and tree type of the current coding unit,
The transform coefficients for the current coding unit are derived by quantizing residual samples for the current coding unit based on the chroma QP,
The CU chroma QP offset-related information is signaled as transform unit syntax for the first transform block among transform blocks of the current coding unit,
A transmission method, characterized in that the CU chroma QP offset related information is obtained based on that at least one of the width and height of the current coding unit is greater than 64 and the tree type is not dual tree luma.

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